I am very new to emacs so it would be a big help if answers came with a lot of detail.
I've tried to get my M-x shell to run python 3 but can't. I've tried:
(setq python-shell-interpreter
"/Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6")
and also adding this location to ~/.emacs but neither have worked. I have python 3.6 installed and running in terminal but can't get it running in the M-x shell. I'm using a mac.
M-x shell gives you an emacs buffer that mostly behaves as a regular shell terminal. That means that when you issue a command, like find, grep or python, it searches through your system path and runs the first program it finds that matches the name you used. The variable python-shell-interpreter has nothing to do with this.
Which means, on your system, the executable for python is pointing to python 2, not python 3. You'll have to fix this outside of emacs. Or you can explicitly set it within M-x shell if you want to make this a temporary change:
alias python=/Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6
You may prefer to directly alter the path.
You could also include code to modify your path, or set up an alias for python, in .emacs.d/init_bash.sh, which is applied every time you run M-x shell.
You can also run your script using python3 script.py too.
M-x shellis for running a shell inside an emacs window. Are you saying that in that shell, when you runpythonyou get python2? An error? What error?M-x run-pythonto get to an interactive repl directly. Down that rabbit hole you'll also learn how to send code directly from a python buffer to the repl, and other stuff that's useful for development